Recent advances in the technology of can manufacturing, such as easy-open ends, improved seam welding, etc., have resulted in a rapidly expanding utilization of cans for the transportation, storage, and dispensation of beverages, foods, and so forth. As can usage has increased, a wide variety of concepts have been devised in attempting to reduce the cost of each individual can so as to provide greater product economy. Such concepts have included further improvements in can seam bonding, reduction in the quantity of metal used in each can, and improvements in the methods and apparatus used for making cans.
One object which has long been pursued by the industry has been to manufacture a can having a satisfactory volume for product containment, a reduced quantity and weight of metal, and a sufficient strength to resist can wall damage. This has been accomplished, to some extent, by the use of aluminum which, due to its ductility, may be drawn to such an extent that a can bottom can be formed integral with the body walls. Use of aluminum allows cans to be produced which have a minimum amount of metal in the walls and a large concentration of metal adjacent to and in the bottom for structural strength.
Relative lack of ductility prevents steel cans from being drawn having integral walls and bottoms, with the resultant material distribution, but the advantages of aluminum are largely offset by the lower cost of steel.
In manufacturing cans today, whether steel, aluminum, or other material, a longitudinal section adjacent each open end of each can body is formed into a generally radially outwardly directed flange. The flange is provided on each open end so that a can end (top or bottom) may be mounted thereon in a well-known manner.
If it is desired to form a can having a diameter of 2-11/16 inches, for example, can bodies are cut and seamed at that diameter. The flanges are then formed at the ends of the can and a 2-11/16 inch can end is suitably fastened to the flange.
When can ends are placed on a body formed in accordance with the prior art, the ends have diameters which are greater than that of the body so that the ends extend beyond the body walls. When two cans are placed next to one another, the can ends are in abutment and the bodies are spaced apart by an amount equal to the difference between the sum of the radii of the can ends and the sum of the external radii of the bodies, thereby resulting in a waste in storage space equal to the total separation between the external wall surfaces of the adjacent cans.
Some aluminum cans having the previously described integral body are provided with a neck just below the flange to increase the wall strength of the can so that it will withstand the forces imposed when a can end is installed on the flange. This also allows a slightly smaller can end to be used, such as a 2-9/16 inch end on a 2-11/16 inch body, and obviates the problem discussed in the last paragraph. However, the necks and flanges for these cans have been provided in two distinct operations, requiring two different machines.
With respect to another aspect of the present invention, several concepts have been developed for the expansion of can bodies into a variety of shapes such as barrels, etc. Many of these concepts have required expensive and cumbersome equipment such as multi-part mandrels, electro-hydraulic shock wave distribution systems, etc. All of these concepts have been directed toward reshaping can bodies to produce commercially attractive containers. None of the prior art has been directed to -- or resulted in -- enlarging of the can body so as to maintain substantially the original body shape while decreasing the weight of the can per unit volume contained therein. Additionally, all of the known prior art has been directed to concepts in which, as the can body is expanded, the axial length of the body is shortened. The results of these concepts have been cans which, while containing a slightly greater volume, do so only because of the fact that they have been reformed into shapes approaching spheres, rather than having been stretched to merely enlarge their original shape.